A Belle Époque purple enamel, diamond and pearl necklace

A Belle Époque purple enamel, diamond and pearl necklace, the central openwork lattice design, set with old and swiss-cut diamonds, to a fine purple guilloché enamelled background, surrounded by a rose-cut diamond-set openwork frame, to a hinged back with locket compartment, suspended from an enamel and pearl chain, with a diamond and enamel background connection, measuring approximately 67cm overall, circa 1900, bearing French hallmarks, gross weight 39.5 grams, circa 1900.